This invention relates to a filtration device for removing precipitable precipitates from liquids such as, e.g., a cleaning liquid used for cleaning an article, a plating liquid, a surface treatment liquid used for cutting, rolling, or the like, a surface treatment liquid used for surface treatment process, and other used surface treatment liquids.
In a conventional filtration method of such liquids as mentioned above, precipitable precipitates are precipitated over a prescribed time in a surface treatment tank in which a surface of an article has been treated and in which a used surface treatment liquid is contained, and a supernatant liquid is recycled.
In another method, a used surface treatment liquid is conveyed by a pump to a precipitation tank arranged separately from the surface treatment tank, the precipitates are precipitated, and the supernatant liquid is recycled.
In another method, the used surface treatment liquid is filtered with a filter material to be recycled.